Certain segments of the container industry have looked, for security purposes, to break-away type closures, i.e., caps having a portion separable therefrom, which remains with the container to indicate initial container opening. For the separable cap portion to remain with the container, containers include a neck having a ridge in interference path with such separable cap portion, and the caps typically include a frangible section adjacent the separable portion, the separable portion itself projecting inwardly to so interfere.
Two approaches are noted in the prior art to providing the required interference between the container neck and the cap separable portion. A first practice involves molding a cap in such configuration that its separable portion does not interfere with the container neck upon threading of the cap onto the container. Then, heat is applied to the cap separable portion and it is deformed mechanically onto the container neck below a projecting ridge. This first practice, shown for instance in U.S. Pat. No. 3,673,761, has disadvantage in requiring a step after assembly, i.e., combined heat application and mechanical deformation. Further, as is noted in the '761 patent, the application of heat need be selectively controlled to protect the cap frangible section from distortion adversely affecting its later functioning.
A second practice involves the molding of a cap with its separable portion in radially inwardly projecting orientation to serve to interfere with the container neck ridge directly upon assembly. Such cap structure is seen, for example, in U.S. Pat. No. 2,162,712.
Since, in the latter practice, the closure separable portion is of lesser interior diameter than the remainder of the closure interior, removal of the cap from its forming core in manufacture presents some difficulty. Thus, stripping or unthreading of the cap from the core, in the absence of radially separable mold parts or collapsible cores, has not heretofore been accommodated to applicants' knowledge, for those plastics providing desired cap strength and hardness. Radial separation of mold parts has attendant disadvantages, e.g., same requires an additional time-consuming, profit-reducing step, and there are increased mechanism costs to effect mold part separation. Related disadvantages likewise attend the use of collapsible cores.